I have a super weird problem in a SharePoint online environment.
I tried various things but at the end got to the conclusion that any changes that I am affecting to the master page, are being updated on every account but hers. This is neither a cache nor a browser problem. I tried on different browsers and on different computers. It seems that SharePoint is caching the master page for that particular account. I also tried changing the master page. Naturally the alert does not show on the different master page but comes back again when reverting back to the actual master page.
But this does not add up! I don't know where to start from. I cannot delete the user and start again as this is a work email with a lot of important mail!